21655390263 has 16 divisors (see below), whose sum is σ = 31119340896. Its totient is φ = 13315927680.

The previous prime is 21655390249. The next prime is 21655390297. The reversal of 21655390263 is 36209355612.

It is a happy number.

It is not a de Polignac number, because 21655390263 - 2⁴ = 21655390247 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655390243) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 167608 + ... + 267213.

It is an arithmetic number, because the mean of its divisors is an integer number (1944958806).

Almost surely, 2^21655390263 is an apocalyptic number.

21655390263 is a deficient number, since it is larger than the sum of its proper divisors (9463950633).

21655390263 is a wasteful number, since it uses less digits than its factorization.

21655390263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 436114.

The product of its (nonzero) digits is 291600, while the sum is 42.

The spelling of 21655390263 in words is "twenty-one billion, six hundred fifty-five million, three hundred ninety thousand, two hundred sixty-three".